This invention relates to a method of manufacturing a waterproof wire harness in which a grommet-passing portion of a wire bundle for passing through a grommet, adapted to be mounted in a through hole in a body panel of a vehicle, is tied into a waterproof structure in which a gap between any adjacent wires is closed by a water sealing agent.
FIG. 6 shows a first related-art method of manufacturing a waterproof wire harness.
The wire harness 1, shown here, is used in the electric wiring for a vehicle, and when a group of wires are shaped into a form to be wired on the vehicle, a waterproofing treatment is applied to those portions of the wires which are to be passed through a grommet 3 adapted to be mounted in a through hole formed in a body panel of a vehicle.
More specifically, first, the grommet 3 is mounted on a predetermined portion of the wire bundle 4 as shown in FIG. 6A, and then a water sealing agent 6 in an unsolidified state is filled in a gap between an inner surface of a harness-passing hole 3a in the grommet 3 and the wire bundle 4 as shown in FIG. 6B, and is allowed to stand for a predetermined time period, so that the water sealing agent is solidified, thereby providing a waterproof structure in which the gap between the wire bundle 4 and the grommet 3 is filled up by the solidified water sealing agent 6, as shown in FIG. 6C.
In such a manufacturing method, however, a very small gap remains between any adjacent wires at the grommet-passing portion of the wire bundle 4, and therefore there is a fear that external rain water intrudes into these gaps because of a capillary phenomenon, which has invited a problem that a sufficient waterproof effect can not be obtained.
Therefore, there has been proposed a second related-art manufacturing method shown in FIGS. 7 through 8F.
The waterproof wire harness-manufacturing method, shown here, is disclosed in Japanese Patent Publication No. 10-135657A, and a waterproofing treatment jig 13 is beforehand mounted on a predetermined portion of a wiring operation board 11 which is used for preforming or shaping a group of wires into a form to be wired on a vehicle.
A plurality of wire group support jigs 15a, 15b, 15c, 15d, 15e, . . . for supporting the wire group in a branched pattern, corresponding to the predetermined wiring form, are mounted on the wiring operation board 11.
The waterproofing treatment jig 13 has slits 13c for arranging the wires of the grommet-passing portion in a row, each of the slits being defined by a pair of opposed arms 13a and 13b. 
The width of the slit 13c is so determined as to arrange the wires of the grommet-passing portion vertically one upon another in one row.
The waterproof structure of the grommet-passing portion, utilizing the waterproofing treatment jig 13, is formed according to the procedure of FIGS. 8A to 8F.
Namely, first, grommet-passing portions of the group of wires 16 are arranged vertically in a row like a belt by the pair of spaced-apart slits 13, as shown in FIG. 8A. Then, a water sealing agent 19 in an unsolidified state is applied to one surface of that portion of the arranged wire group 16, disposed between the pair of slits 13c, by a coating nozzle 18 as shown in FIG. 8B. Generally, moisture-solidifying silicone RTV is used as the water sealing agent 19. Then, a band-like film 21 for uniting purposes is bonded to the one surface of the wire group 16, coated with the water sealing agent 19, thereby interconnecting the wires of the wire group 16 in such a manner that these wires are kept arranged in one row, and thereafter the waterproofing treatment jig 13 is moved downward, thereby removing the wire group 16 from the waterproofing treatment jig 13, as shown in FIG. 8C.
Then, the band-like film 21 is wound on the wire group 16 to tie this wire group into a wire bundle of a round cross-section, as shown in FIG. 8D. Further, a tape 23 is wound on that portion of the wire bundle, tied by the band-like film 21, thereby forming the wire bundle into such a circular cross-sectional shape and size that the wire bundle can be tightly fitted into a harness-passing hole in a grommet, as shown in FIG. 8E, and the water sealing agent is solidified. Thereafter, the grommet 25 is mounted on that portion of the wire bundle having the tape 23 wound thereon, as shown in FIG. 8E.
In the above manufacturing method, however, in the case where the wire group includes wires of different outer diameters, it has sometimes been difficult to arrange the wires in one row, and besides it has been difficult to coat the water sealing agent onto the wire group.
When the arrangement of the wires and the coating of the water sealing agent are effected satisfactorily, a gap between any adjacent wires at the grommet-passing portion of the wire bundle can be filled up by the water sealing agent. Even in such a case, however, when the group of wires 16 are tied into a bundle by the band-like film 21, the outer diameter of the resulting wire bundle is liable to vary, and in the next step of winding the tape 23, the outer diameter of the wire bundle must be corrected into a size, corresponding to the diameter of the harness-passing hole in the grommet 25, by adjusting the amount of winding of the tape 23. Thus, the operation for adjusting the amount of winding of the tape 23 is required, and therefore there have been encountered problems that much time and labor are required for the operation, and that it is difficult to carry out the operation in an automated manner.
And besides, when the tape 23 is wound spirally, there is a probability that very small gaps are formed in step portions, formed by the overlapping portions of the wound tape 23, thus lowering the waterproof performance.